Common side effects include: feeling tired, diarrhea and feeling restless. More serious side effects include: movement disorder like tardive dyskinesia, a condition called neuroleptic malignant syndrome, and depression.[2] It is thus rarely recommended that people take the medication for longer than twelve weeks.[2] It is pregnancy category B in the United States and category A in Australia, meaning no evidence of harm has been found after it being taken by many pregnant women.[2][4]

Clinicians commonly use metoclopramide to treat nausea - including that due to chemotherapy and that occurring postoperatively. Evidence also supports its use for gastroparesis (poor stomach emptying) and gastroesophageal reflux disease.[2]

The Rosemont Patient Information Leaflet of their sugar-free metoclopramide hydrochloride (5 mg/5 ml) oral solution states, " Metoclopramide can be used to treat stomach upset including heartburn, wind, pain, indigestion, sickness and bile regurgitation, to stop nausea and vomiting, to relieve your symptoms of nausea and vomiting when you have a migraine, to help restore normal stomach emptying after an operation and during hospital tests such as a barium meal." and "In young adults and children, metoclopramide can be given for severe and long-lasting vomiting if the cause is known, to stop vomiting caused by cancer treatment such as radiotherapy and chemotherapy, to help in passing a tube into the stomach and intestine and to help stop feeling and being sick before having an operation." [10]

Metoclopramide may be the most common cause of drug-induced movement disorders.[13] The risk of extrapyramidal effects is increased in people under 20 years of age, and with high-dose or prolonged therapy.[7][8] Tardive dyskinesia may be persistent and irreversible in some patients. The majority of reports of tardive dyskinesia occur in people who have used metoclopramide for more than three months.[13] Consequently, the US Food and Drug Administration (FDA) recommends that metoclopramide be used for short-term treatment, preferably less than 12 weeks. In 2009, the FDA required all manufacturers of metoclopramide to issue a black box warning regarding the risk of tardive dyskinesia with chronic or high-dose use of the drug.[13]

In some cases, the akathisia effects of metoclopramide are directly related to the infusion rate when the drug is administered intravenously. Side effects were usually seen in the first 15 minutes after the dose of metoclopramide.[16]

Metoclopramide is contraindicated in pheochromocytoma. It should be used with caution in Parkinson's disease since, as a dopamine antagonist, it may worsen symptoms. Long-term use should be avoided in patients with clinical depression, as it may worsen one's mental state.[8] Also, it is contraindicated in patients with a suspected bowel obstruction.[2]

A systematic review found a wide range of reported outcomes for treatment of gastroesophageal reflux disease (GERD) in infants and concluded a "poor" rating of evidence and "inconclusive" rating of safety and efficacy for the treatment of GERD in infants.[21]

The antiemetic action of metoclopramide is due to its antagonist activity at D2 receptors in the chemoreceptor trigger zone in the central nervous system — this action prevents nausea and vomiting triggered by most stimuli.[24] At higher doses, 5-HT3 antagonist activity may also contribute to the antiemetic effect.

The gastroprokinetic activity of metoclopramide is mediated by muscarinic activity, D2 receptor antagonist activity and 5-HT4 receptor agonist activity.[25][26] The gastroprokinetic effect itself may also contribute to the antiemetic effect. Metoclopramide also increases the tone of the lower esophageal sphincter.[27]

Metoclopramide is contraindicated in case of epilepsy, if a stomach operation has been performed in the previous three or four days, if the patient has ever had bleeding, perforation or blockage of the stomach, in cases of pheochromocytoma, and in newborn babies.[10]